Thursday, September 15, 2011

ViewSonic VX2235wm and ADSL issues

I know this is a true story because it happened to me.

On a non robot slant I got to do some consumer electronics repairs recently. I have a 22" wide screen monitor on my main desktop, a ViewSonic VX2235wm. The desktop is five plus years old but still working well and more than enough of the odd internet cruising and mplab activities. The hard drive was starting to throw bad sectors so we decided to upgrade the machine to Windows 7 and replace the old hard drive. The wife installed Windows 7 fine. Everything was going along fine until we tried to access the internet. No joy. The Netgear ADSL wireless modem would drop it's internet connection whenever this desktop was on. Booting back to the XP setup, same issue. We also remembered the last time this desktop was on the laptop lost internet connection, but previously things had been fine.

We found that when the desktop goes on, 30 seconds later the internet connection gets dropped. Desktop goes off, internet come back. Wacky power issues?

Then I triggered it wasn't when the desktop came on, it was when the monitor came on. After replacing power cables things still weren't working. Different power circuits, still the same issue. We ran an extension lead from the 15Amp circuit in the shed, same issue. In all this time the monitor was working fine. The picture was fine, no odd behaviour.

Powering down the monitor and trawling the internet the wife found this monitor suffered from the common "bad capacitor" issue. Various electronics components get made with substandard capacitors which leak, fail, etc well before they are expected to. Based on what we were reading the wife suggested that I try and fix the monitor. At first I was reluctant to take apart a working monitor in case I made the issue worse and would be unable to fix it. However as the wife pointed out the monitor was useless as we lost the internet connection every time we turned it on. To the shed.

Taking apart the monitor was easier than expected. A few screw and then some gentle prying with a flat tip screw driver popped off the case. I didn't even break any of the snap together lugs. My daughter helped out by poking things with a screwdriver. A few more screws and the power supply circuit board was accessible. Three seconds later it was obvious what the issue was. The 400V 120uF capacitor had a nice blob of black goo coming out of it. Without that capacitor a large amount of electrical noise would be going back into the power line. This noise was so great it caused the ADSL modem to lose sync. Glad I've already had kids.

400V capacitors aren't stocked by the normal hobby electronics stores I go to like Jaycar, etc. Instead I went online to RS Components for the part, mainly as they were offering free shipping. $8 and a week and half later I had the replacement part. Out the old and in with the new. After putting the case back together I did a smoke test and the smoke stayed in. Taking the monitor back inside and turning it on, success! No more drop outs of the ADSL line. Happy days again. Now the wife can finish setting up the rebuilt desktop.

I can't see how electronic repair shops stay in business. For even a simple job like this the time cost alone would be the price of a new monitor. So next time you need a monitor check the skip bins. An hour, a soldering iron and some capaciors later you might have a working monitor.

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